The invention herein is a further improvement of related subject matter contained in the cross-referenced prior patent applications, which prior patent applications are relied upon for priority rights in previously described novel features.
Computer systems are becoming increasingly more portable while at the same time becoming increasingly more powerful. Low power consumption is an essential design criterion of portable battery powered computer systems and data terminals. For this reason much of the hardware in a portable computer system, such as the system microprocessor, operates at lower logical voltage supply levels, typically 3.3 volts or even 2.7 volts, because systems operating at lower voltages consume less power than systems operating at higher voltages. The most common computer hardware devices operate at 5.0 volts for logic voltage levels. Portable data terminals and other laptop type computer systems employ microprocessors and other hardware devices which operate at 3.3 volts or 2.7 volts for logic voltage levels in order to reduce system power consumption and thereby extend operational battery time.
As the logical switching speeds of computer systems increase, the amount of heat generated as a result also increases. It is for this reason that microprocessor chip manufacturers have needed to lower the logical operating voltages with increased processor speeds because even with heat sinks and fans to cool them, high operating speeds combined with high voltages will cause the chip to overheat.
If proper thermal management of the electronics of a portable electronic device are not carefully considered and engineered for, catastrophic thermal failure may occur resulting in a total loss of electronic function. In general, for a capacitive load, the relationship between the power generated by an electronic device and the operational voltage and frequency is given as: EQU P.varies.v.sup.2 .multidot.f
where P is the power generated, v is the operational voltage and f is the operational frequency. Therefore, with increased operational frequencies, it is desirable to correspondingly decrease the operational voltage in order to minimize the power (and thereby the heat) generated by the electronic device. However, the dichotomy of decreasing the operational voltage of an electronic device operating at high frequencies is that the switching speeds of electronic devices operating at lower voltages are slowed as a result of the lower voltages. Thus, it is difficult to obtain high frequency operation of an electronic device with simultaneous low power operation.
Because maintaining low power consumption and preserving battery energy are important design criteria in portable data terminal systems, the dynamics of delivering power in multiple supply logic voltage computer systems must be taken into account. For example, the powering up of the system hardware devices requires more power than the average power consumed during normal operations, and therefore it is of great advantage to preserve battery energy by minimizing power consumption during system startup. A prudently designed power supply system for mixed logic voltage level computer hardware may consider the order in which the devices are powered up and the system hardware is reset.
Electronic devices are often rated according to their speed-power product, which is the average switching time multiplied with the average power dissipation. Energy may be conserved in multiple supply logic voltage computer systems by dynamically altering the clock speed of the system according to the processing needs of the system. By keeping the clock speed nominally low and increasing the speeds when applications demand higher speeds, the amount of energy generated and dissipated by the electronic systems may be minimized. Additionally, energy may be conserved by dynamically altering the operational logic voltage levels accordingly with required operational clock speed. Operational power levels above average rated power levels may be attained for momentary periods without damage to the electronic systems.
For the foregoing reasons, there is a need for a power supply system in multiple logic voltage computer systems that dynamically varies the logic voltage levels and operational frequency at which the particular circuitry operate according to the demands of a particular application in order to minimize power consumption in a hand held portable electronic system.
Thus, despite the intense efforts of those skilled in the art, there still exists a need for a power supply which is capable of dynamically switching the operational voltage and operational frequency in a multiple logic voltage level electronic system.